Chevy 700-R4 Transission Build - 700 Soup-Up

Jet Performance Transmissions Builds One Strong Overdrive

Since its introduction by General Motors back in 1982, the venerable 700-R4 automatic overdrive transmission has found its way into more early American iron than we care to count. Part of the reason for its popularity is its gearing characteristics-low first and second for those inevitable rabbit starts, plus a very pleasing 30 percent overdrive, which significanty lowers engine rpm during freeway cruising. Now, as with anything performance-oriented, OEM equipment can come up short in certain areas, and Jet Performance Transmissions has sought out all the weak links of the 700-R4 and developed a virtually bulletproof trans with a variety of options and applications.

Jet's T-700 transmission (its modified version of the 700-R4) features all of the standard GM options, but has been improved upon to produce firmer, more responsive shifts. Jet also offers the transmission in a non-lockup version, which we will showcase here. The converter in this model is stall-matched to each individual engine. A variety of things are done to improve the transmission, such as the addition of extra (heavy-duty) clutches, a Corvette servo to eliminate band slippage, and bigger, stiffer springs throughout. The clutch band is eliminated in the non-lockup converter, and shims are used to prevent premature wear or failure.

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Our victim 700 trans was stripped down and given a good bath prior to being built up.

The reason behind a non-lockup overdrive is the ability to get more out of the four-speed transmission in all gears. Instead of the 700 hunting for overdrive at certain speeds or rpms, it features positive, firm shifting throughout. Instead of being "stuck" in lockup on the freeway, you can simply press on the throttle a bit more and get responsive acceleration every time rather than having to hit it hard to drop down into third. With a higher-stall converter, launching off the line is greatly improved, as well. Basically, you get benefits on both ends of the performance spectrum. Obviously there will be some enthusiasts who prefer the characteristics of the lockup trans, which is why Jet offers high-performance versions of it as well.

Instead of rambling on about the ins and outs of the Jet Performance Transmissions T-700 overdrive, follow along with the accompanying photos and see what tricks they've perfected to get the most out of this popular transmission.

MORE PHOTOS

Our victim 700 trans was stripped down and given a good bath prior to being built up.

The stock low reverse clutch pack is rebuilt with a larger sprag (left), shown next to a stock sprag.

Jet takes every precaution to avoid any type of failure in their transmissions, so each T-700 is built with brand-new sun shells. Used ones have a tendency to crack easier under harder use.

The 3-4 clutch pack is modified with extra clutches (usually nine compared to six) for more holding power and nice, firm shifts. Blueprinting clutch clearances here is critical. (The stock clutch pack is shown to the right.)

The forward clutch pack is next to be assembled...

...and blueprinting is important here, as well.

The 3-4 clutch pack (with extra clutches) goes together in the same fashion.

The reverse drum is rebuilt with new, heavy-duty clutches and steels. The outside surface is sanded (to remove any glazing), providing more holding power for the band.

Next up is the pump modification. Along with a non-lockup converter, the pump has to be reworked, and a few extra holes do the trick.

First, a 1/8-inch bit is used to create a lube hole for added fluid flow.

Setscrews are added to hold the lockup valve in place, which eliminates the lockup valve spring.

The goal is to keep the lockup valve in the forward position, as indicated.

The pressure regulator is modified to prevent the buzzing noise found in some situations.

Larger pressure regulator boost valves (left) are installed to increase the line pressure.

Next, a stiffer slide spring is installed, again to firm up the shifts.

A 10-vein rotor with hardened rings in installed in the pump for increased durability.

Once completely rebuilt and checked, the assembled input drum is re-installed in the trans case.

With the drum fit and checked, the pump is then installed.

Another upgrade featured on the T-700 is the addition of a Corvette servo with stiffer springs, which provides firmed shifting.

The servo is installed in the case and checked for clearance.

The modification work then progresses to the bottom of the transmission. First, the fourth gear accumulator and spring are installed.

The valve body plate is then drilled out to provide better fluid flow.

After the plate is drilled and cleaned, it is installed with the 1-2 accumulator (which has stiffer springs).

Prior to any upgrades, the entire valve body is inspected for free-moving valves throughout, and any necessary repairs made.

The non-lockup conversion requires that the fourth-gear pressure switch be removed and replaced with a brass plug.

Although it can be left intact, a faulty switch will cause serious malfunction and premature failure.

The culmination of the firmed-up shifting improvements is a stiffer throttle-valve spring.

Nearing the end of the buildup, the valve body is re-installed in the transmission with the proper gasket.

With a new filter and pan gasket, all that's left before the T-700 is put on the dyno are the tailshaft parts.

The governor is installed with a new gear and checked for free valve movement. (The output shaft shown here is actually a shorter, 4WD unit; the standard shaft is longer, with a typical tail housing.)